2 MOTILE STAGES OF CHRYSOCHROMULINA-POLYLEPIS (PRYMNESIOPHYCEAE) - MORPHOLOGY, GROWTH, AND TOXICITY

Eight months after the 1988 bloom of Chrysochromulina polylepis Manton et Parke in Skagerrak and Kattegat, off the coasts of Norway, Sweden, and Denmark, an alternate cell type carrying a scale complement different from that of authentic C. polylepis appeared in some clones isolated from the bloom. The cultures were recloned, and the development of the new clones was monitored. In clones with 100% cells of the alternate type, authentic cells reappeared, suggesting that the alternate cell type is a stage in the life cycle of C. polylepis and that transition between cell types occurs in both directions. Growth rates of clone cultures (termed alpha-cultures) producing exclusively authentic cells, and of clone cultures (termed beta-cultures), capable of producing the alternate cell type, were compared at various combinations of temperature and photon fluence rate. The beta-cultures were less tolerant of high temperatures and photon fluence rates (greater-than-or-equal-to 20-degrees-C, 570-mu-mol photons.m-2.s-1) than were the alpha-cultures. At lower temperatures and photon fluence rates (less-than-or-equal-to 16-degrees-C, less-than-or-equal-to 90-mu-mol photons.m-2.s-1), beta-cultures grew better than alpha-cultures. Relative abundance of the two cell types in beta-cultures changed in an apparently random manner during these experiments. Preliminary results from flow cytometric analyses indicated that cells of the alternate type were about twice the size and contained an equal or smaller amount of DNA per cell compared to the authentic cells. The beta-cultures were less toxic to Artemia nauplii than were the alpha-cultures. Three other Chrysochromulina species tested were apparently nontoxic.